The Pittsburgh Southern Railway was a narrow gauge railroad in Pennsylvania. It was formed in March 1879 by the merger of the Pittsburgh Southern Railroad (which was named the Pittsburgh, Castle Shannon and Washington Railroad from July 1877 to April 1878), Pittsburgh Railroad, and Washington Railroad. It ran from Washington to Castle Shannon, where it connected to the Pittsburgh and Castle Shannon Railroad

Pittsburgh and Castle Shannon Railroad

The Pittsburgh and Castle Shannon Railroad was a narrow gauge railroad in Allegheny County, Pennsylvania. Originally built in 1871, it may have been the first American common carrier narrow gauge railroad. It purchased a rail line called the Coal Hill Coal Railroad from the Pittsburgh Coal...

. An attempt to use the Little Saw Mill Run Railroad

Little Saw Mill Run Railroad

The Little Saw Mill Run Railroad was a standard gauge coal railroad in Allegheny County, Pennsylvania. It was incorporated July 23, 1850, and opened in April 1853. Originally, it was owned by the Harmony Society, and ran from Temperanceville, Pennsylvania on the Ohio River to Banksville,...

 as a substitute connection to Pittsburgh led to the Castle Shannon Railroad War of 1878.

It was converted to standard gauge

Standard gauge

The standard gauge is a widely-used track gauge . Approximately 60% of the world's existing railway lines are built to this gauge...

 in 1883, and was purchased by the Baltimore and Ohio Railroad

Baltimore and Ohio Railroad

The Baltimore and Ohio Railroad was one of the oldest railroads in the United States and the first common carrier railroad. It came into being mostly because the city of Baltimore wanted to compete with the newly constructed Erie Canal and another canal being proposed by Pennsylvania, which...

 on November 20, 1884 and reorganized as the Baltimore & Ohio Short Line Railroad

Baltimore & Ohio Short Line Railroad

The Baltimore and Ohio Short Line Railroad was the successor to the Pittsburgh Southern Railway, and a subsidiary of the B&O Railroad, and was organized as a legal entity 25 February, 1885. The railroad was a link in the attempt of the B&O to serve the Pittsburgh market, and became part of the...

.